fan stairway
A spreading stairway with angles or bends in individual steps, producing a fan-like or amphitheater-like arrangement.
A fan-shaped stairway is a set of stairs without a single direction, which spreads out from bottom to top or from top to bottom, with angles or bends in the individual steps. If a stairway spreads out but retains a single direction, with straight steps parallel to each other, then it is generally classified as belonging to the closest other configuration.
The stairway can widen upward or downward. Its individual steps change direction rather than remaining straight parallel lines.
A widening flight with straight parallel steps is expressly assigned to the closest other configuration. Width variation by itself does not establish the fan form.